To gain insight into the spread of hepatitis B among various risk groups in Amsterdam a 6-year (1992-1997) retrospective DNA sequencing study was carried out on isolates from stored sera from reported primary cases of acute hepatitis B infection. Cases were classified according to risk behavior, as determined in interviews. Of the available serum, a selected region of hepatitis B-virus-DNA was amplified and sequenced. The nucleotide alignments were subjected to phylogenetic tree analysis. When nucleotide alignments were subjected to phylogenetic analysis, the strains of 54 isolates, 26% of the 204 reported primary cases, clustered in five genotypes: A, C, D, E, and F. In genotype A, a cluster related to men having sex with men was identified. In genotype D, two subclusters could be identified: one was related to injecting drug use and another was related to the Moroccan population in Amsterdam. The remaining strains showed a high genetic variability within three different genotypes: F, E, and C. Of the 14 identical isolates in the "homosexual men cluster," one was isolated from a female heterosexual. Of the 14 identical strains in the "drug users strain," six were from non-drug using heterosexual active individuals. In the cluster of twelve isolates related to hepatitis B-endemic areas, probable modes of transmission were varied. Sequence analysis provides important insight into the spread of hepatitis B among various high-risk groups. The analysis indicates that the prevention strategy in The Netherlands fails to stop transmission of hepatitis B from persistently infected individuals originating from hepatitis B endemic countries.

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SummarySelf-reported compliance with a malaria chemoprophylaxis regimen of proguanil (PG) plus chloroquine (CQ) was assessed in a cohort of 547 Dutch travellers who visited a single travel clinic when travelling to various areas endemic for falciparum malaria. 503 (92%) had taken PG/CQ prophylaxis, but only 326 (60%) reported regular and uninterrupted use throughout the journey and 4 weeks afterwards. Compliance differed by travel destination and was 45% in South America, 52% in West Africa, 53% in South-east Asia, 60% in the Indian Subcontinent and 78% in East Africa. Parasitologically confirmed falciparum malaria occurred in 5 travellers (0.9%), including 3 of 24 non-compliant travellers to West Africa (12.5%). Apart from destination, independent risk factors for non-compliance were young age, extensive travel experience and adventurous travel. Compliance with protection against mosquito bites was 80% for wearing long-sleeved shirts and long-legged trousers after sunset, 73% for use of repellents, 56% for sleeping under bednets and 37% for keeping the sleeping quarters free of mosquitoes. Although 440 travellers (80%) reported to have taken two or more of these measures at least once, only 88 (16%) had done so on a daily basis. Daily use of bednets was reported more frequently among subjects who were non-compliant with chemoprophylaxis. Compliance regarding malaria chemoprophylaxis should be improved, particularly in high-risk areas such as Sub-saharan Africa, with extra attention to young, adventurous travellers. More emphasis should be placed on prevention of Anopheles bites.

Titres of antibodies against hepatitis A virus (HAV) were determined in patients, in donors, and in volunteers after active, passive, and combined immunization. Highest titres were found in recently infected persons: in 109 IgM anti-HAV positive persons, the geometric mean titre (GMT) was 15,400 mIU/ml. The GMT in 265 anti-HAV positive blood donors was 10,700 mIU/ml. The anti-HAV seroprevalence in 19,746 donors increases with age: at the age of 40 years, 50% have antibodies. Titres after active, passive, and combined immunization were studied in three groups: 51 persons received inactivated HAV vaccine at months 0, 1, and 6. The GMT after the booster was 3,400 mIU/ml at month 7. All persons produced more than 100 mIU/ml anti-HAV. Forty-nine persons received both 5 ml immunoglobulin and three vaccinations, yielding a GMT of 1,300 mIU/ml at month 7. One person in this group produced less than 100 mIU/ml anti-HAV. Forty-nine persons received 5 ml immunoglobulin intramuscularly. At day 5 the GMT was 96 mIU/ml. The estimated minimum protective level (10 mIU/ml) was reached in 3 months. Hepatitis A vaccination may supersede the use of immunoglobulin as prophylaxis for travellers to endemic areas. Passive immunization remains necessary for protection during outbreaks. The dosage regimen for passive immunization is based on old studies using preparations with unknown anti-HAV content. Concern regarding the antibody levels in immunoglobulin preparations is justified; the prevalence of HAV antibodies in developed countries continues to fall. Our results indicate that dosage regimens should be reconsidered. Dosage should be deduced logically from the anti-HAV antibody content of the immunoglobulin preparation.